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Background: Bone conduction hearing aids can be worn as noninvasive devices using a clip or soft band that exerts pressure on the skin, or they can be surgically implanted. ADHEAR (MED-EL GmbH, Innsbruck, Austria) is a novel noninvasive bone conduction hearing aid that is attached behind the ear using an adhesive adapter and does not exert pressure on the skin. ADHEAR is indicated for patients with conductive hearing loss and normal inner ear function. The aim of this study was to evaluate the achievable hearing improvement with ADHEAR., Materials and Methods: Twelve subjects with normal hearing participated in this study. To mimic conductive hearing loss, the participants' ear canals were occluded unilaterally with a foam ear plug. The resultant conductive hearing loss was assessed with pure tone air- and bone-conduction threshold audiometry. Hearing ability was tested with and without ADHEAR via free-field tone audiometry, number perception, and monosyllable perception, with the contralateral ear plugged depending on test requirements., Results: Using ADHEAR, the free-field hearing threshold improved by 13.7 dB at 500 Hz, by 17.9 dB at 1 kHz, by 17.2 dB at 2 kHz, and by 9.8 dB at 4 kHz. In the higher frequencies, a significant pure-tone gain of 14.4 dB at 6 kHz and of 16.5 dB at 8 kHz was observed. Number perception with ADHEAR was mean 69.2% at 35 dB, 97.9% at 50 dB, 100% at 65 dB, and 100% at 80 dB. Monosyllable perception with the ADHEAR was mean 35.0% at 35 dB, 72.3% at 50 dB, 93.5% at 65 dB, and 98.8% at 80 dB., Conclusion: Hearing performance was significantly better with ADHEAR under all test conditions except those where maximum perception was already achieved without ADHEAR.